Boiling points esters

The use of a solvent to extract phenol from carbon has been more successful. Mackert53 percolates benzene through the carbon bed to displace the phenol and water from the carbon. The phenol collects in the benzene layer and is subsequently separated by distillation. The benzene remaining on the carbon is removed by low-pressure steam. Other eluting solvents that have been employed are alcohol, chlorinated hydrocarbons, low-boiling-point esters, ammonia, and sodium hydroxide. 

In Chapter 1, section 3 there is an account of the behaviour of rubber polymers. The brittle holder is an interesting example of control of Tg by means of the plasticizer content of a PVC composition. One of the important effects of plasticizer is to lower Tg. Unplasticized or rigid PVC, as used in rainwater goods and window frames has a Tg of 80 C. Addition of plasticizer (usually high boiling point esters) lowers Tg progressively, and softens the material. The effect is to impart elastomeric, or rubber, properties. Fig. 3.3 shows this. 

The diamine used is MDA salt, which is a sodium chloride complex of methylene dianiline. Above 120 C the salt dissociates, to give a very fast cure - 3 min. An example of the difficulties which can arise in specific industries and applications is given by the fact that the MDA salt is supplied as a 30% solution in dioctyl phthalate (DOP). DOP is incompatible with the developed PU system, and can exude under mechanical pressure to attack the primer. No satisfactory solution to this problem has yet been found, because MDA, like its predecessor methylenediorthochloroaniline (MOCA) is regarded as a toxic material, and is only supplied in this form. DOP is a very non-volatile high-boiling point ester, and this minimizes the vapour pressure and hence concentration in the air of MDA during transport and use. 

Plasticizers are added to PVC compounds in order to confer flexibility and softness. The plasticizers most commonly employed are high boiling point esters of Cg.io alcohols such as phthalates, phosphates and sebacates. Examples of common plasticizers are dioctyl phthalate (DOP, which is also known as 2-ethylhexyl phthalate), di-iso-octyl phthalates (DIOP) and, dialphanyl phthalate (DAP). 

Drying by hydrolysis. The production of extremely dry (99 -9-(- per cent.) ethyl alcohol from commercial absolute alcohol (99-f percent.) is possible by taking advantage of the fact that the hydrolysis of an ester consumes water. Thus if the absolute alcohol is treated with a little sodium in the presence of an ester of high boiling point e.g., ethyl... 

If, however, the sodium hydroxide is removed by allowing it to react with excess of an ester of high boiling point, such as ethyl succinate or ethyl phthalate, super-dry ethyl alcohol may be obtained ... 

Place 200 g, (250 ml.) of rectified spirit in a 1-litre round-bottomed flask fitted with a reflux condenser. Cool in ice and run in, slowly and with frequent shaking, 200 g. (109 ml.) of concentrated sulphuric acid. Add 83 g. (104 ml.) of -butyl cyanide (Section 111,113) to the mixture and reflux the whole for 10 hours. Allow to cool, pour the reaction mixture into ice water, separate the upper layer of ester and alcohol, and dry over anhydrous magnesium or calcium sulphate. Distil through a fractionating column and collect the ethyl n-valerate at 143-146°. A further amovmt of the pure ester may be obtained by redrying the fraction of low boiling point and redistilling. The yield is 110 g. 

In Table 111,106 the boiling points, densities and refractive indices of a number of selected esters are collected. 

Aromatic esters usually burn with a smoky flame, possess reasonably high boiling points, and are (particularly esters of phenols) sometimes crystalline solids. Phenyl esters usually give phenol upon distillation with soda hme (see Section IV,175 for general details). 

Section 20 8 Esters are polar and have higher boiling points than alkanes of compa rable size and shape Esters don t form hydrogen bonds to other ester molecules so have lower boiling points than analogous alcohols They can form hydrogen bonds to water and so are comparable to alcohols m their solubility m water... 

One of the hydroxybenzoic acids is known by the common name salicylic acid Its methyl ester methyl salicylate occurs in oil of wintergreen Methyl salicylate boils over 50°C lower than either of the other two methyl hydroxybenzoates What is the structure of methyl salicylate Why is its boiling point so much lower than that of either of its regioisomers ... 

Methyl salicylate is the methyl ester of o hydroxybenzoic acid Intramolecular (rather than mtermolecular) hydrogen bonding is responsible for its relatively low boiling point... 

Dichloroacetic acid is produced in the laboratory by the reaction of chloral hydrate [302-17-0] with sodium cyanide (31). It has been manufactured by the chlorination of acetic and chloroacetic acids (32), reduction of trichloroacetic acid (33), hydrolysis of pentachloroethane [76-01-7] (34), and hydrolysis of dichloroacetyl chloride. Due to similar boiling points, the separation of dichloroacetic acid from chloroacetic acid is not practical by conventional distillation. However, this separation has been accompHshed by the addition of a eotropeforming hydrocarbons such as bromoben2ene (35) or by distillation of the methyl or ethyl ester. 

Ester CAS Registry Number Pressure, kPa Boiling point, °C... 

Alcoholysis (ester interchange) is performed at atmospheric pressure near the boiling point of methanol in carbon steel equipment. Sodium methoxide [124-41 -4] CH ONa, the catalyst, can be prepared in the same reactor by reaction of methanol and metallic sodium, or it can be purchased in methanol solution. Usage is approximately 0.3—1.0 wt % of the triglyceride. 

Fig. 5. Solubility coefficient at 30°C versus boiling point of ester in a low density polyethylene film (18). For unit conversion see equation 6.

The higher fatty acids undergo decarboxylation and other undesirable reactions when heated at their boiling points at atmospheric pressure. Hence they are distilled at reduced pressure (15,16). Methyl esters boil at lower temperatures than acids at the same pressure as the result of the absence of hydrogen bonding (17). A procedure for calculation of the vapor pressures of fatty acids at various temperatures has been described (18). 

Esters of high volatility, such as methyl formate, methyl acetate, and ethyl formate, have lower boiling points than those of the corresponding alcohols, and therefore can be readily removed from the reaction mixture by distillation. 

Applications. Transesterifications via alcoholysis play a significant role in industry as well as in laboratory and in analytical chemistry. The reaction can be used to reduce the boiling point of esters by exchanging a long-chain alcohol group with a short one, eg, methanol, in the analysis of fats, oils, and waxes. For more details see References 7 and 68. A few examples are given below. 

Isothiazole-4,5-dicarboxylic acid, 3-phenyl-dimethyl ester synthesis, S, 150 Isothiazole-5-glyoxylic acid ethyl ester reduction, 6, 156 Isothiazole-4-mercurioacetate reactions, 6, 164 Isothiazole-5-mercurioacetate reactions, 6, 164 Isothiazoles, 6, I3I-I75 acidity, 6, 141 alkylation, 6, 148 aromaticity, S, 32 6, 144-145 basicity, 6, I4I biological activity, 6, 175 boiling points, 6, I43-I44, 144 bond fixation, 6, 145 bond orders, 6, I32-I34 calculated, 6, 133 bromination, S, 58 6, 147 charge densities, 6, 132-134 cycloaddition reactions, 6, 152 desulfurization, S, 75 6, 152 deuteration, S, 70... 

In many cases simple esters are more easily purified than their intractable parent acids. For example, /7-xylene is difficult to obtain in pure form because of the closeness of its boiling point to the other isomeric xylenes (o-144°C m- 138.8°C p- 138.5°C). It is thus difficult to produce terephthalic acid, which sublimes at 300°C, in a pure form. 

Chemical Designations - Synonyms Epoxidized tall oil, octyl ester Chemical Formula Mixture. Observable Characteristics - Physical State (as shipped) Liquid Color. Pale yellow Odor Mild. Physical and Chemical Properties - Physical State at IS X and 1 atm. Liquid Molecular Weight 420 (approx.) Boiling Point at 1 atm. Not pertinent Freezing Point Not pertinent Critical Temperature Not pertinent Critical Pressure Not pertinent Specific Gravity (est.) 1.002 at 20 °C (liquid) Vcpor (Gas) Specific Gravity Not pertinent Ratio of Specific Heats of Vcpor (Gas) Not pertinent Latent Heat of Vaporization Not pertinent Heat of Combustion Data not available Heat of Decomposition Not pertinent. 

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